2011 Jeep Wrangler Unlimited - Brake trouble

replaced brake master cylinder and still have no brakes. bled system 3 times. brake pedal still goes to floor and will not hold

hmmm … when you press on brake pedal, brake fluid should immediately pressurize and pedal only go a little ways down. In your case either

  • brake pedal not pushing on mc push rod plunger
  • brake fluid is leaking out somewhere
  • brake fluid has air pockets
  • wheel cylinders/caliper pistons not engaging brake shoes/pads.
  • replacement brake MC faulty

If no signs of brake fluid leaks, and wheel components were working ok before MC replaced, and presuming replacement MC ok, most likely there’s still air in the brake lines. Does your Jeep have ABS? If so, sometimes it is very difficult to air-bleed that system without the aid of a ABS-compatible scan tool, that allows opening and closing the ABS valves on command. Some makes more than others, don’t know how much this applies to your vehicle.

I’m just a diyer, older cars, no ABS, but never had any problems with my brake bleeding method. I start with the longest brake line (usually right rear), open the bleeder valve, then push very gently on the brake pedal with my hand (not foot), put a stick on the pedal so it won’t go back up, then close the bleeder. Allow pedal to gently return. Repeat until no air bubbles come out. Usually only takes 3 or 4 pushes per wheel. Some here say the gravity bleed method is pretty fool-proof. With it you just open the bleeder and let the fluid leak out by the force of gravity. Takes considerably longer, but seems like it would pretty much guarantee all the air gets expelled eventually.

Some posters here claiming brake bleeding difficulty realize the problem is they’ve replaced something in the brake system incorrectly. Putting brake calipers on the wrong side is a common mistake. That causes the bleeder valve to point down, which of course will be impossible to air-bleed.

Maybe you could explain the background; i.e. why did you replace brake master cylinder?

Did you bench bleed the master cylinder before installing? You should have.

Did you loosen the brake lines at the master with someone pushing the brake pedal to bleed the highest point in the system?

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Anytime the brake system is opened and air is allowed to enter the system, the ABS must also be bled using a scan tool.